This invention relates to electrolysis apparatus, especially for the electrolysis of water, and is applicable to apparatus for producing oxyhydrogen gas (detonating gas) and to apparatus producing oxygen and hydrogen at separate outlets. The invention in concerned with improved cooling of the apparatus and electrolyte.
My British patent application No. 7,914,972 relates to a simple construction of apparatus for generating detonating gas, comprising a plurality of parallel-disposed electrode plates clamped together with a ring-shaped spacer between each pair of electrodes: the space between each pair of electrodes, and enclosed by the spacer, defines a cell. A d.c. electrical supply is connected across the two outermost electrode plates so as to connect the plurality of cells in series. Fresh electrolyte is supplied through an inlet to one end cell and electrolyte and generated gas flow from cell-to-cell (through apertures formed through the electrode plates near the top of the cells) until the final cell, where the detonating gas leaves by way of an outlet, mixed with a certain amount of electrolyte.
In any electrolysis apparatus having a plurality of cells arranged in series both on the electrical and electrolyte flow paths, the electrolyte and gas increase in temperature from cell-to-cell through the apparatus towards the outlet. The rate of gas generation increases with the current flowing, but so also does the heat generated. The electrolyte entering any cell (after the first) is the already-heated electrolyte from the previous cell, so that with many cells arranged in series a limit temperature might well be reached, where the electrolyte entering the next cell is too high. In my British patent application No. 7,914,972, cooling is provided for in that the electrode plates project outwardly beyond the spacers and the surfaces of these projecting portions of the plates are available for cooling by ambient air or by pre-cooled air (forced cooling).
By making the electrode plates thicker to increase heat flow and increasing the surface areas in contact with the cooling air, heat dissipation can be improved. Appropriate choice of metals also assists cooling: electrodes of copper plated with nickel are effective. Less costly steel electrodes, also nickel plated, have lower heat conductivity, leading to poorer cooling: increasing the thickness of these electrodes to improve heat flow leads to increased weight and cost. Another appropriate metal is stainless steel and this does not require a nickel coating at low electrolyte temperatures: however, if higher temperatures do occur, then the stainless steel will be attacked by the hot electrolyte.
It is generally desirable, therefore, to improve the cooling and enable higher rates of gas generation. Improved rates of hydrogen or hydrogen-and-oxygen generation are of particular interest in the development for the future of hydrogen engines for cars. Hydrogen may be stored, at ambient temperature and avoiding very high pressures, in iron-titanium pellet tanks: the hydrogen is absorbed by crystals of iron-titanium within a tank and the hydrogen is not released accidentally even if the tank is punctured. Experimental cars being developed on this principle lack a low-cost, high-rate hydrogen generator able to produce sufficient hydrogen over night to re-charge a spent tank. Such generators might even be installed in the household. Experimental cars to date demonstrate a range of about 200 kilometers before a full hydrogen tank requires re-charging, if the car is driven under reasonable conditions. The capacity of the tank corresponds with 32000 liters of hydrogen at ambient temperatures. In accordance with Faraday's law, a current of 26.8 amps flowing for one hour will produce 11.2 liters of hydrogen and 5.6 liters of oxygen. As an example of a household generator, working from a 380 volts a.c. supply, a rectified supply of 380 volts d.c. may be produced without using a transformer; this could feed an apparatus having 190 cells in series (each with the usual voltage drop of about 2 volts). With a current of 100 amps flowing, the equivalent is 19,000 amps flowing through a single cell, generating 19,000.div.26.8.div.11.4=8082 liters of hydrogen in one hour. Thus the tank of 32,000 liters would be re-charged within 4 hours: or, for example, a current of 50 amps would re-charge the tank in 8 hours.
Because the tank accepts only hydrogen, the generator must either produce hydrogen separated from oxygen, or the oxygen must be eliminated from the detonating gas eliminated for example by using it up in an appropriate chemical reaction, or by employing a molecular sieve or other means for separating gases.
A detonating gas generator, such as the apparatus disclosed in my British patent application No. 7,914,972, does generally operate with lower heat losses than does an apparatus producing oxygen and hydrogen separately, because the path of the electrical current through the electrolyte can be kept very short. Also, the cell construction is much simpler because there is no need for a diaphragm to divide the cell into oxygen and hydrogen sections. Nevertheless, this invention is applicable both to a detonating gas generator and to an apparatus for generating oxygen and hydrogen separately.